Such an apparatus for so-called “bin picking” is known from WO 2010/024794 A1. In this apparatus, a resilient element is arranged between the gripping arm and the gripper as a compensation unit which allows a certain movement of the gripper on a load on the gripper due to a collision, for example. In this respect, a control is provided which measures and/or controls the elastic deformation of this element.
The resilience of the element between the gripping arm and the gripper is in this respect intended to make it possible that on an inaccurate traveling of the gripper toward a workpiece, the gripper is deflected on the basis of the collision with the workpiece such that it can still pick the workpiece. Only when a certain deformation of the resilient element is exceeded should the picking procedure be stopped.
It is disadvantageous in this arrangement that a deformation of the resilient element not only takes place on a collision with an interfering edge, but also due to the gripper's and/or the workpiece's own weight so that the exact position of the gripper depends on the deformation of the resilient element and can therefore only be determined with difficulty. The position of the gripper can in this respect in particular only be determined by an accurate measurement of the deformation of the resilient element. An exact monitoring of the deformation is furthermore also necessary for the decision whether the picking procedure should be stopped. In addition, the arrangement is prone to problems.
It is therefore the object of the present invention to provide an improved apparatus for the automated handling of workpieces.
This object is achieved in accordance with the invention by an apparatus in accordance with claim 1. Advantageous embodiments of the invention form the subject of the dependent claims.
The apparatus in accordance with the invention for the automated handling of workpieces comprises an object recognition device for detecting the workpieces, a gripper arranged at a gripping arm for picking the workpieces and a control for evaluating the data of the object recognition device, for track planning and for controlling the gripping arm and the gripper. The control can in this respect in particular comprise an evaluation device for evaluating the data, a track planning module for track planning and a control unit for controlling the gripper. A compensation unit is furthermore provided which allows an evasion movement of the gripper. In accordance with the invention, the compensation unit, however, only allows an evasion movement of the gripper on an exceeding of a predefined first load on the gripping arm, while it remains rigid below the first load. In accordance with the invention, the first load is in this respect larger than a load exerted on the gripping arm only by the gripper and/or by the picked workpiece. In accordance with the present invention, in particular no evasion movement of the compensation unit thus takes place despite the load on the gripping arm by the gripper's and, where applicable, the workpiece's own weight.
It is therefore ensured by the compensation unit in accordance with the invention and unlike by the resilient element used in the prior art that the gripper adopts a defined position with respect to the gripping arm in normal operation. The position of the gripper in normal operation is hereby unambiguously defined so that a secure and accurate moving of the gripper via the gripping arm becomes possible.
The first load is in particular selected so high that this load limit can only occur, at least in a travel position of the gripper, by a collision of the gripper with an interfering edge such as the workpiece to be picked and/or another workpiece and/or a side wall of a container.
The apparatus in accordance with the invention can in this respect in particular serve the removal of workpieces randomly arranged in the container since the position of the workpieces can be determined by a suitable object recognition device and therefore does not have to be known in advance. The apparatus can naturally, however, also be used when the workpieces are already present with a certain order in the container.
In accordance with the invention, any desired system which allows the identification of the workpieces and the selection of a workpiece suitable for picking can be used as an object recognition device for detecting the workpieces.
The detection of the workpieces in this respect typically comprises a data logging by a measurement process. An identification of the individual workpieces in the detection zone from which a workpiece suitable for picking is selected then takes place by evaluating the data. The movement of the gripper or of the gripping arm moving it is planned on the basis of the positional data of this workpiece. In this respect, a collision check can be carried out so that a movement routine is selected in which the gripper or the gripping arm does not collide with interfering edges such as the other workpieces and/or the side walls of the container. The gripper or the gripping arm is then controlled using the data thus calculated.
In this respect, in particular optical sensors are used as the object recognition device, with in particular laser sensors and/or image sensors being able to be used. The sensors can in this respect work two-dimensionally, two-and-half-dimensionally and three-dimensionally. A 3D laser scanner is particularly preferably used in this respect.
A sensor arrangement is furthermore advantageously provided which recognizes an evasion movement of the compensation unit occurring due to a collision on an exceeding of the first load.
The sensor arrangement can in this respect, for example, comprise a contact sensor and/or an optical sensor.
Further advantageously, a predefined travel path of the gripping arm is permitted on detecting a collision. The picking procedure is hereby not interrupted, for example, when the gripper comes into contact with the workpiece to be picked.
In this respect, the picking position of the gripper can be calculated so that no direct contact usually arises between the gripper and the workpiece by the traveling of the gripper toward the workpiece. The still permitted travel path in this case secures the system against an unnecessary stop if a collision does still occur, for example due to inaccuracies in the detection of the workpiece or in the control of the gripping arm.
Provision can alternatively be made that the picking position is calculated so that a direct contact between the gripper and the workpiece arises by the traveling of the gripper toward the workpiece. The detection of the collision thus allows a check as to whether the gripper was traveled into the correct position.
Provision can furthermore be made that the gripper is traveled toward a workpiece for so long until a collision is detected.
Irrespective of the manner of the traveling of the gripper toward a workpiece, the gripper can be moved back again after the picking up of the workpiece initially on the same path with which it was traveled toward the workpiece. Since this path has not produced any collisions on the traveling, the probability that no collisions will also arise on the traveling back is particularly high in this respect.
Furthermore, in a possible embodiment, the data of the sensor of the compensation unit can remain out of consideration for a certain travel path on the lifting of the workpiece so that a deflection of the compensation unit in this region is not evaluated as a collision. It can hereby in particular be avoided that dynamic and/or static loads on the picking up of the workpiece, which result in a deflection of the compensation unit, are erroneously evaluated as a collision.
Provision can furthermore be made in accordance with the invention that individual portions of the gripping arm movement are carried out at different speeds. The gripping arm can in particular be traveled at a lower speed in regions in which a collision has to be expected than in regions in which a collision does not have to be expected.
The gripping arm is in this respect advantageously traveled at a first speed for so long as the gripper is located outside the container for the workpieces and at at least one second, lower speed for so long as the gripper is located within the container. Further advantageously, the gripper is furthermore traveled at a third, still lower speed in a near region to the workpieces and/or interfering edges. The gripper can in this respect in particular be traveled a certain path distance at the third speed before a picking procedure takes place or before the gripper is traveled to the workpiece.
As already described above, the picking procedure does not have to be directly stopped in accordance with the invention when a compensation movement of the compensation unit was detected. The picking procedure can rather utilize the compensation path of the compensation unit in order also to be able to carry out a further movement after the detection of a compensation movement.
This compensation path can furthermore be utilized to brake the gripping arm in good time before the total compensation path of the compensation unit was used up despite corresponding processing times and control times.
The picking procedure is in this respect advantageously stopped and restarted on the exceeding of a permitted travel path which corresponds to a second load of the gripping arm.
If, in contrast, it is detected that a collision is no longer present before the permitted travel path was exceeded, the operation can be continued without interruption.
In this respect, in accordance with the invention, the magnitude of the evasion movement does not have to be known to initiate a reaction to a collision. The travel path from the detection of the collision known from the control of the gripping arm is rather utilized for this purpose. A monitoring of the deformation of the compensation unit is thus not necessary in accordance with the invention.
The adjustment path of the gripping arm which the control allows after the detection of a collision is advantageously smaller than the compensation path of the compensation unit. It is hereby ensured that on a movement of the gripping arm in the permitted adjustment region, the forces occurring by the collision are taken up by the compensation unit.
On the determination of the permitted travel path, the processing time of the control and the reaction times of the drives of the gripping arms can be taken into account in this respect to ensure a braking in good time within the compensation path of the compensation unit.
The control in this respect advantageously has an overload function which intervenes on the exceeding of a predefined third load of the gripping arm, with the third load being larger than the first and/or second loads. The overload function can in this respect in particular be the overload function of a robot arm. Provision can furthermore be made that the overload function works with reference to the monitoring of the load of the drives of the gripping arm. Provision can furthermore be made that the overload function caries out an emergency stop on recognition of an overload so that the gripping arm can only be released again by a manual user intervention.
The compensation unit in accordance with the invention now prevents such a high load acting on the gripping arm that the overload function intervenes. In particular only a travel path is permitted on detection of a compensation movement and thus of a collision of the gripper with an interfering edge by which the load does not increase beyond the first load.
The gripper is advantageously moved back into a neutral position on the exceeding of the permitted travel path and the picking procedure is restarted. In this respect, in particular a repeat detection of the workpieces to be picked can take place before a workpiece is again picked.
The traveling back of the gripper after the detection of a collision can in this respect first take place on the reverse path with which the gripper was moved up to the collision.
The sensor arrangement of the compensation unit can also be configured such that the direction of a compensation movement is recognized. The control advantageously takes account of this direction of the compensation movement thus recognized on the retraction of the gripper. It can in particular thus be prevented that the load of the gripping arm increases by the retraction.
The apparatus in accordance with the invention can furthermore have a force torque sensor arrangement arranged separately from the compensation unit at the gripping arm for measuring the load of the gripping arm. This combination of compensation unit and force torque sensor arrangement thus allows an exact monitoring of the load of the gripping arm and nevertheless ensures by the rigid design of the compensation unit in accordance with the invention that a defined position of the gripper is present at the gripping arm in normal operation.
In a further embodiment, the apparatus in accordance with the invention can comprise two compensation units connected in series. This in particular makes it possible to increase the compensation path provided by the compensation units.
The first compensation unit is in this respect advantageously a compensation unit having a spherical compensation movement, while the second compensation unit is a compensation unit having a linear compensation movement. The protective function against loads in any directions provided by the spherical compensation unit can hereby be combined with a large compensation path provided by the linear compensation unit.
Provision can furthermore be made that the two compensation units are preloaded via separate preload means. The loads at which the two compensation units deflect can hereby be separately determined.
Provision can further preferably be made that the two compensation units deflect at different loads of the gripping arm. Provision can in this respect in particular be made that the linear compensation unit only deflects when the spherical compensation unit has already previously deflected.
In this respect, the sensor arrangement which detects a deflection of the compensation unit is advantageously arranged at the compensation unit which deflects on the lower load of the gripping arm and/or at the compensation unit having a spherical compensation movement.
The sensor unit for recognizing the deflection of the compensation unit can further preferably only detect the deflection movement of one of the two compensation units, while a compensation movement of the other compensation unit is not monitored.
In this respect, different possibilities result in dependence on the application for the configuration of the first load of the gripping arm at which the compensation unit or, on the use of a plurality of compensation units, at which the first compensation unit deflects:
On the one hand, the compensation unit can be configured so that the first load at which it deflects is larger than the static loads which are exerted on the compensation unit independently of the position and orientation of the gripper by the gripper as well as a by a workpiece arranged at the gripper. The compensation unit can optionally also be set so that dynamic loads, for example on the starting or accelerating of the gripper, also do not result in a deflection of the compensation unit. It is hereby ensured that the compensation unit actually only triggers on collisions.
However, such a configuration is not always possible, in particular with heavy grippers and/or workpieces and/or with loads in normal operation which come relatively close to the maximum permitted load of the gripping arm.
Alternatively, the compensation unit can therefore also be configured such that it admittedly remains rigid without a picked up workpiece independently of the position and orientation of the gripper, but optionally also deflects without a collision with a picked up workpiece and/or on dynamic loads.
The control of the apparatus in accordance with the invention is in this case preferably configured such that a deflection of the compensation unit is not necessarily evaluated as a collision. The control is further preferably designed such that static loads of the gripper after the picking up of the workpiece are reduced within a predefined travel path.
In this respect, the control can be designed so that the gripper changes the orientation of the gripper after the picking up of a workpiece with a slanted gripper such that the static forces are reduced which are exerted on the compensation unit by the gripper's own weight and by the weight of the workpiece. The present invention in this respect makes use of the recognition that the maximum static forces on the compensation unit occur at a position of the gripper in which it is deflected to the side by 90° and becomes lower with smaller deflections with respect to the vertical. An oblique orientation of the gripper can in this respect be necessary on the picking up of the workpiece. After the lifting of the workpiece, however, it is possible as a rule to move the gripper back in the direction of the vertical to reduce the static loads.
The gripper is therefore advantageously directed downwardly into a travel position after the picking up of a workpiece and is in particular oriented in the vertical direction. The gripper in this respect advantageously remains in the travel position during the travel path with which the workpiece is removed and placed down elsewhere.
The change in the orientation in this respect advantageously takes place on the lifting of the workpiece. In this respect, in particular with an obliquely aligned gripper, the travel movement of the gripper on the lifting of the workpiece can correspond to the travel movement of the gripper toward the workpiece and can be superimposed with the pivot movement by which the gripper is rotated in the travel position. In this respect, in particular the traveling toward the workpiece or the lifting of the workpiece takes place in the direction of the orientation of the gripper on picking.
Provision is advantageously made in this respect that the deflection of the compensation unit on the lifting is not evaluated as a collision. It is hereby prevented that a deflection is erroneously evaluated as a collision due to the static and/or dynamic loads which arise on the lifting. In this respect, the signal of the sensor of the compensation unit in a certain travel region after the start of the lifting of the workpiece is advantageously not taken into account.
In accordance with the invention, a compensation unit having two compensation units connected in series, as was described above, is particularly preferably used with a magnetic and/or pneumatic gripper. Such a compensation unit can, however, also be used with a mechanical gripper.
In a further aspect, the present invention comprises an apparatus for the automated removal of workpieces arranged in a container comprising an object recognition device for detecting the workpieces and a gripper arranged at a gripping arm for picking and removing the workpieces from the container as well as a control for evaluating the data of the object recognition device, for track planning and for controlling the gripping arm and the gripper. In accordance with the invention, the gripper is a magnetic and/or pneumatic gripper in this respect.
This embodiment of the gripper in accordance with the invention has the advantage that the gripper allows larger tolerances on the movement of the gripper into a picking position relative to the workpiece. In this respect, in particular a plurality of positions can be suitable for picking a workpiece so that the workpieces can be picked more securely.
In this respect, an object recognition device can be used as the object recognition device for detecting the workpieces such as was already described above with respect to the object recognition device for detecting the workpieces in the previously described aspect of the present invention.
The evaluation of the data, identification and selection of the workpieces, the track planning and the control of the gripper of the positioning apparatus can also take place in a similar manner as has been represented above with respect to the corresponding steps.
The object recognition device for detecting the workpieces in the container is in this respect preferably arranged in its measurement position above the container.
In the selection of the workpiece to be picked, it can in particular be detected in this respect whether a workpiece was identified which can be picked with a predefined first relative position between the workpiece and the gripper.
Such a first relative position can in particular represent an ideal picking position between the workpiece and the gripper which comprises the fact with a magnetic gripper, for example, that the magnetic surface of the gripper overlaps ideally with the workpiece.
However, the case can arise with parts not lying on one another in order than none of the workpieces present in the container can be picked with such a first relative position. In accordance with the invention, the control can in this case select a workpiece which is picked with a second picking position, for example a not ideal picking position. With a magnetic gripper, for example, a certain offset can be allowed in this respect between the magnetic gripping surface and the workpiece. A picking position rotated by an angle with respect to the ideal magnetic picking position can likewise be considered as an alternative picking position with the magnetic gripper, for example having an angle offset of 90°. Alternatively, or also when this is not possible, a picking can be attempted at the highest point of the workpiece, for example. A plurality of alternative picking positions can in particular be provided which are used in the selection of the workpiece to be picked.
Provision can alternatively or additionally be made that the gripper is controlled in accordance with the invention such that for the case it cannot pick up a workpiece with a first position calculated for picking, it repeats the picking with a second, changed position.
Provision can in particular also be made here to pick a workpiece to be picked with an offset or at its highest position when a sufficient cover cannot be achieved between the gripping surface of the gripper and a main surface of the workpiece.
However, it cannot be ensured with a magnetic or pneumatic gripper that the gripper actually only picks up a single workpiece. The case can in particular namely occur with the magnetic gripper that the gripper picks up two or even more workpieces.
The apparatus in accordance with the invention can furthermore have a force torque sensor arrangement for measuring the load of the gripping arm. The force torque sensor arrangement can in this respect in particular be arranged at the gripping arm separately from an above-described compensation unit.
The control can in this respect recognize by an evaluation of the data of the force torque sensor arrangement whether and how many workpieces can be picked up. The weight of a workpiece or the loads exerted on the force torque sensor arrangement in normal operation by this weight are in particular stored in the control for this purpose and can thus be compared with the loads actually occurring on the picking of a workpiece. Alternatively, the determination whether and how many workpieces were picked up can also takes place by the monitoring of the gripping force and/or of the current or power required to operate the gripper, in particular with a magnetic gripper.
Provision can be made in this respect that the control reduces the gripping force of the gripper when, for example, it is recognized via the data of the force torque sensor arrangement that more than one workpiece was picked up. The magnetic and/or pneumatic gripper also has the advantage in this respect that the gripping force can be set flexibly. In this respect, in particular with the magnetic gripper, the power of the griper electromagnet can be reduced. An attempt can be made by the reduction of the gripping force in this respect to drop the excess workpieces from the gripper again. In this respect, the gripping force can advantageously be reduced for so long until it is recognized with reference to the data of the force torque sensor arrangement that only a certain number of workpieces, and preferably only one workpiece, was picked up at the gripper.
Furthermore, the picking procedure can in particular be repeated using the data of the force torque sensor arrangement when it is recognized that no workpiece was picked up on a picking procedure.
The apparatus in accordance with the just described second aspect of the present invention, in which a magnetic and/or pneumatic gripper is used, can in this respect preferably be combined with the first described aspect of the present invention, i.e. with a compensation unit in accordance with the invention.
The demands on the delivery accuracy or the gripper to a workpiece can hereby be kept small and the load of the gripping arm, which is unwanted on a collision which nevertheless occurs, and/or the necessity of a manual intervention can be avoided.
The two aspects of the present invention can in this case each be used on their own or also combined with an apparatus in which the gripper removes the workpieces from a container and places them on an intermediate station from where the workpieces are positioned more accurately and/or are singularized via a positioning apparatus. This is in particular of particular advantage when a magnetic and/or pneumatic gripper is used since it does not allow any accurate positioning of the workpieces at a target receiver.
In this case, an embodiment is preferably used having two compensation units connected in series, in particular a two-stage compensation unit such as was described above.
A gripper in accordance with the first aspect of the present invention having a compensation unit in accordance with the invention can, however, also be used in accordance with the invention as a positioning apparatus for the more accurate positioning of a workpiece, starting from an intermediate station. In this respect, a mechanical gripper can in particular also be used.
In this case, an embodiment is preferably used having only one compensation unit, in particular having a spherically working compensation unit such as was described above.
The workpiece can advantageously be removed from the container by a first gripper and placed down on the intermediate station, with the workpiece advantageously being dropped onto the intermediate station from a certain height. A slanted plane can in particular be provided in this respect onto which the workpieces are dropped. The workpieces can in this respect slide to a further transport position on this slanted plane.
Furthermore, a transport device can be provided on the intermediate station which transports the workpieces from a placing region to a removal region. The positioning apparatus advantageously removes the workpieces in the removal region by the positioning apparatus in this respect, with a gripper, in particular a mechanical gripper, advantageously being provided for picking the workpieces in the removal region.
In this respect, a repeat detection of the workpieces advantageously takes place on the intermediate station by which detection the positioning apparatus, and in particular a gripper of the positioning apparatus, can be controlled. In this respect, in particular an object recognition device for detecting the workpieces is arranged in the removal region.
In accordance with the invention, the workpieces can thus be placed randomly arranged on the intermediate station and can nevertheless be accurately picked due to the repeat detection.
The present invention furthermore comprises a compensation unit having a base unit and a compensation plate which is engaged around by a holding region of the base unit and is preloaded toward the base unit and in particular the holding region via a spring arrangement so that the compensation unit only allows an evasion movement between the base unit and the compensation plate on an exceeding of a predefined first load and remains rigid under the first load.
Such a compensation unit can in this respect in particular be used between a gripping arm and a gripper in accordance with the invention in order, as described above, to prevent an overload of the gripping arm on a collision of the gripper with an interfering edge.
The compensation unit is in this respect preferably configured and is used as was described in more detail above with respect to the apparatus.
Further advantageously, one or more sensors are provided, in particular in the holding region, which monitor the lying of the compensation plate at the holding region. In this respect, it can, for example, be one or more contact sensors and/or optical sensors. The sensors can thus recognize whether the compensation unit carries out a compensation unit since the first load was exceeded or whether the compensation unit is rigid. In this respect a plurality of sensors can preferably be provided so that the direction of the compensation movement can be recognized.
The compensation plate is round in a preferred embodiment. This allows a compensation movement in all directions by a slanted position of the compensation plate. Further advantageously, a margin of the compensation plate is rounded to prevent a canting of the compensation plate.
Further advantageously, the compensation plate is arranged non-rotatably at the base unit in order hereby to prevent rotational movements of the compensation plate.
The movement between the base unit and the compensation unit can in this respect in particular allow a spherical compensation movement.
In a preferred embodiment, the compensation unit further comprises a second compensation unit which allows a linear compensation movement.
Provision can be made in this respect that the two compensation units are preloaded via separate preload means. Provision can further be made that the two compensation units deflect at different loads of the gripping arm.
The second compensation unit can in this respect in a possible embodiment have one or more bars which are linearly guided in a guide and are preloaded via a spring.
In this respect, the spherical compensation unit and the linear compensation unit are advantageously connected in series.
Further advantageously, the spherically working compensation unit deflects first and only then the linearly acting compensation unit.
The present invention furthermore comprises a method for operating an apparatus for the automated handling of workpieces which has an object recognition device for detecting the workpieces and a gripper arranged at a gripping arm for picking the workpieces as well as a control for evaluating the data of the object recognition device, for track planning and for controlling the gripper arm and the gripper as well as a compensation unit which only allows an evasion movement of the gripper on an exceeding of a first load of the gripping arm. In accordance with the invention, the first load is in this respect selected larger than the forces occurring in the normal operation of the gripper, with the compensation unit remaining rigid under the first load so that evasion movements of the gripper are prevented in normal operation. The first load can in this respect in particular be selected as larger than the load exerted on the gripping arm only by the gripper and/or by the picked workpiece.
It is ensured by the method in accordance with the invention that in normal operation an unambiguous positional relationship is present between the gripper and the gripping arm and evasion movements of the gripper only occur on a collision.
In this respect, in accordance with the method in accordance with the invention a collision is advantageously recognized by the detection of an evasion movement and the still permitted travel path on the detection of a collision is restricted. If this travel path is also exceeded, the picking procedure is stopped and restarted.
The method in accordance with the invention is advantageously carried out in this respect as has already been described in more detail above with respect to the apparatus in accordance with the invention. The method in accordance with the invention in particular serves in this respect the operation of an apparatus as was described above.
Provision can furthermore be provided that the orientation of the gripper is changed after the picking up of a workpiece with a slanted gripper such that the static forces acting on the compensation unit due to the gripper's own weight and the weight of the workpiece are reduced. The gripper is in this respect preferably oriented in a travel position into which it is oriented downwardly, and in particular downwardly in a vertical direction.
The change in the orientation in this respect advantageously takes place on the lifting of the workpiece. Further preferably, the deflection of the sensor on lifting is not evaluated as a collision.
The present invention further comprises a method for operating an apparatus for the automated removal of workpieces arranged in a container comprising an object recognition device for detecting the workpieces and a gripper arranged at a gripping arm for picking and removing the workpieces from the container as well as a control for evaluating the data of the object recognition device, for track planning and for controlling the gripping arm and the gripper. Provision is made in this respect in accordance with the invention that the workpieces are picked magnetically and/or pneumatically.
The load of the gripping arm can advantageously be measured in this respect. Provision can in particular be made in this respect that the gripping force of the gripper is reduced when it is recognized that more than one workpiece is picked up.
The method in accordance with the invention can furthermore take place as has already been described above with respect to the apparatus in accordance with the invention. The method in accordance with the invention in particular serves in this respect the operation of an apparatus as was described above.
The present invention furthermore comprises a computer program for carrying out one of the methods which were described above. The computer program in particular comprises commands for this purpose which implement the method on an apparatus for the automated handling of workpieces arranged randomly. The computer program in accordance with the invention can in this respect in particular be used for implementing a control for an apparatus as was described above.
All the steps in the handling of the workpieces advantageously take place by the method in accordance with the invention and/or by the apparatus in accordance with the invention in a fully automated manner and without a user intervention being necessary.
The subject of the present invention will now be described in more detail with reference to embodiments and to drawings.